c reactive protein is present when a person is ill and is suffering from some kind of infection. since he is already suffering u can complete the prescribed by yr doc.. also give him more of fluid based diet, soups, juices at room temperature, light cereals, light dals , fruits rich in vitamin C and increase protein intake.. here is a blog u would find useful. avoid force feeding.. and serve him whatever he feels like having.
https://www.parentune.com/parent-blog/diet-during-fever-in-your-child/3812?ptref=sa0l0010f8502xw

Actually my son is suffering with fever, cold and cold from 31st of August. I went to doctor on that day itself, he gave antibiotic cold cough and fever syrups all got cured to some extent but not completely. today fever was 98. 7 so as it is third day we asked for blood test in that c reactive protein test result was 13. 8. So as there is improvement he told to continue same medicines. But i want to know what is the cause for infection and what care what food i should give to my son to reduce infection? due to god grace he is active